In general, a post-processing apparatus is an apparatus that is disposed to be adjacent to an image forming apparatus (e.g., a copier, a printer, or the like) or is disposed inside the image forming apparatus so as to perform a post-processing task, such as stapling or the like, with respect to paper periodically discharged from the image forming apparatus.
A user may preset paper discharged from the image forming apparatus to a paper set including at least 2 or more sheets of paper so as to enable the post-processing apparatus to post-process the paper according to each paper set. The post-processing apparatus continuously compiles conveyed paper to a compiling region and then, if paper is compiled by a preset paper set, immediately performs a post-processing task in the compiling region. If the post-processing task is completed, the post-processing apparatus discharges the post-processed paper set and continuously compiles a next paper set conveyed from the image forming apparatus in the compiling region.
However, if the image forming apparatus discharges paper at a high speed faster than or equal to 50 ppm, the post-processing apparatus does not compile paper that is conveyed in response to a processing speed of the image forming apparatus due to a post-processing task taking a preset time. In order to solve this problem, the post-processing apparatus is to overcome a speed difference from the image forming apparatus by using a method of allowing first paper of each paper set to pre-stand by before a post-processing task of a previous paper set is completed.
If an existing large post-processing apparatus is disposed to be adjacent to an image forming apparatus so as to enable a user to set 2 sheets of paper to one paper set through a method as described above, the existing large post-processing apparatus may operate to a speed corresponding to about 85% of a speed of the image forming apparatus. On the contrary, an existing embedded post-processing apparatus made in a small size does not use a method as described above due to a space restriction. Therefore, if an embedded post-processing apparatus is installed and used inside an image forming apparatus performing high-speed processing, productivity of the embedded post-processing apparatus is lowered.
Also, even if an existing post-processing apparatus complies a plurality of paper sets according to a method of allowing first paper of a paper set to pre-stand by as described above, a skew phenomenon where leading ends of first paper and second paper keep a distance from each other occurs. Therefore, first paper of each paper set is not appropriately stapled to other sheets of paper.